12au7 tube?

Do you ever somehow try to musically match 12AU7 driver and power output tubes in advance or it is just a matter of experimentation? I mean, if I am lucky at some point and get a set of EL34 Mullards should I also consider replacing 12AU7 RCA blackplates driver tubes with Mullards ?

No I do not ever try to match brands of tubes together nor have I ever thought about that neither do I see any benefit to it. Almost all of my equipment is operating with all different brands of tubes. Even though I had Mullard MCI 12ax7’s as input tubes, my favorite 12ax7 is the Amperex long plate double DD getter. But at the time of evaluating the EL34’s, I had the Mullards in the input. The Mullard MCI btw are some of the best 12ax7’s ever made.  In the beginning, Depending on the type of tube equipment I’d own in the past, I usually was very curious at how much improvement in sound I could get by picking up premium tubes that were favorites by many audiophiles that were in the hobby before me. Slowly I began purchasing tubes and listening to them in my amplifiers to hear what they sounded like and to satisfy my curiosity. Nowadays when I’m in need of a specific or special sound I’m hoping to achieve, I have some of my favorite tubes to put in place and see if it helps. Ive been in this hobby for 30 plus years and I already know by listening to a system if it’s good or if it’s lacking. I only swap tubes today if I hear a problem. If it sounds good, I change nothing. My ears tell me when something is transparent, revealing, airy, engaging, natural, and all the beautiful things we want to hear from our systems. If I purchase a new piece of equipment that has Chinese tubes, I very much might keep those tubes in as long as it sounds transparent and good. When I purchased my Conrad Johnson Premier Four, it arrived with 8 Shuguang Chinese EL34’s. First thing I wanted to do was get them out and put something better. But after playing the amp for the first week, I found no issue with the Chinese tubes. To my ears, they sounded great and were doing the trick. So instead of putting in 8 Teslas, I searched for more Shuguang tubes and purchased 16 as backups because in the end, it just sounded fine. I did change out the input and driver tubes on the amp to something better from my vintage stash. I feel setting up a system is a mix of a lot of different stuff. I don’t recommend using the same brand of tubes the same way I wouldn’t recommend using the same brand of cables throughout a system. Building a really nice sounding system is something that is done one step at a time and to get it to be really, really good, it usually takes time tweaking and making little but worthwhile adjustments. It can take yrs till it all finally comes together and the funny thing about this hobby is that when that happens, usually audiophiles still aren’t happy.  I do t think many audiophiles will ever be content or happy with their systems. 

Well, most audiophiles are hard to please and always strive for even better sound than they might already have.

I see, no real reason to think that one tube brand everywhere would have an advantage.

With cables, I think it might depend, though I don't have enough experience to be sure.

I mix match cables and try to use quality cabling. I pretty much don’t use basic cables. I had them in the past, Wireworld, Audio Quest, Cardas, MIT, Tara Labs and so on. I’ve been using newer cables from new companies that sound better to me than cables of the past. I have a limit to what I want to spend on a cable and keep it at that. Today some really nice sounding IC cables can be purchased from $100-$500 pair. Speaker cables as well. Yrs ago not so, for that price only decent sounding but today things have changed and some really good open sounding cables can be purchased at a reason price because we have so much new on the market. I like using silver a lot on my IC’s. I find silver more open, smoother and natural over copper. Thank God I’ve found contentment when I get a setup sounding good. I usually leave it alone and enjoy the music and that’s really what this hobby should be about. But I went through a lot of listening to components, tubes, cables to satisfy my curiosity. 

If you can find a pair of these, grab them. Westinghouse carbon plate 12au7, but a very specific limited production type.

So why this tube is not very well known? It’s very hard to find and even if you find it you have to be careful what you buy. The tube was produced by Westinghouse for a short period of time and after that was sub-licensed from RCA, which didn’t produce the same sound.

Here are the signs of the original WH 12au7:
1) Dots around 12au7 – not the GE type dots, but smaller dot’s in grayish color.
2) Getter must be raised on a copper post above the plate (RCA has them always attached to the plate). For of the getter is Large D with TWO (2) wires attached at the end (RCA only uses one)
3) Silver cover above getter is very extensive (RCA’s is much smaller). This makes it really hard to see the getter. I mean super hard – if you can see it easily, it’s not the real Westinghouse.
4) Plates are not shiny black like RCA, but carbon black. Very unique color – it’s not similar even to Ken-Rad of the same period. It’s like charcoal – a mixture of black and very dark gray. This makes it very hard to distinguish them on pictures – because the color depends on lighting.
5) Yellow color letters with number 337 for the manufacturer – if you are lucky to get silk screen in good shape.